Electric valve circuits



E. E. MOYER 2,273,586

ELECTRIC VALVE cmcurfs Filed July 6, 1940 FigJ.

Feb. 17, 1942.

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Inventor: Elmo E. M0587,

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H i s Attorn e3 Feb. 17, 1942. E. E. MOYER 4 2,273,586

ELECTRIC VALVE cmcuns' Filed July 6, 1940 2 Sheets-Sheet 2 Inventor I H g Attorr e g.

Elmo E. Mo gen' Patented Feb. .17, 1942 UNITED STATES PATENT OFFICE ELECTRIC VALVE CIRCUITS Elmo E. Moycr, Scotia, N. Y-., assignor to General Electric Company, a corporation of New York 13 Claims.

My invention relates to electric valve circuits and more particularly to control systems for electric valve translating apparatus.

In the application of electric valve systems it is frequently desirable to maintain an output voltage within a narrowly defined range of values. For example, in electric valve translating apparatus for battery charging systems, it is important to maintain the voltage impressed across the batteries at a substantially constant value. In accordance with the embodiments of my invention described hereinafter, I providenew and improved control systems which maintain the outapparaput voltage of electric valve translating tus at a substantially constant value. Further, in order to control accurately the output voltage of an electric valve translating apparatus which requires an appreciable amount of grid current for such control, it would be desirable to obtain a wide variation in the phase shift of the grid potentials in response to a very small controlling action. In other words, it would be desirable to control a low impedance grid circuit from a high impedance source. Accordingly I have devised a new and improved phase shifting circuit for accomplishing this result.

It is an object of my invention to provide new and improved electric valve circuits.

It is another of my invention to provide new and improved control systems for electric valve translating apparatus.

feed back arrangement is provided to affect the impedance of the other arm of the bridge to produce an implified phase shift of excitation voltageso that the output voltage is maintained without substantial variation from a constant value. Instead of both variable resistance and variable reactance in a control circuit, a constant resistance and variable reactance may be used or a constant reactance' and variable resistance.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. itself, however, will best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is a diagrammatical rer .esentation of an electric valve converting apparatus embodying my invention; Fig. 2 is a schematic diagram to aid in the understanding of Fig. 1; Fig. 3 represents a modification of a portion of the arrangement illustrated in Fig. 1; Fig. 4 represents still another modification of the apparatus as applied to a battery charger; Figs. 5, 6 and 7 are schematic diagrams to aid in the understanding of the operation of the apparatus illustrated in Fig. 4; and Fig. 8 represents still another modification of my invention.

It is a further object of my invention to provide 7 an improved static phase shifting circuit which is sensitive to a relatively small change in a controlling action or quantity.

In accordance with the illustrated embodments of my invention described hereinafter, I provide new and improved electric valve trans ating circuits for transmitting power from an alternating current supply circuit to a direct current load circuit. The electric valve translating apparatus for accomplish ng this result reouires an appreci able amount of grid or exc tation current for controlling the output voltage. I prov de an improved control system whereby the direct current output voltage is maintained at a su-stantiallv constant value by virtue of a high impedance source of control potential. A pair' of phase shifting bridges is provided. one arm containing a high vacuum electric d scharge valve providing a variable resistance and the other arm containing a variable reactance. The high impedance source of control potentials is applied directly tothe control electrodes of the vacuum type valve to vary the impedance or resistance thereof and a 55 Referring more particularly to the embodiment of my invention shown in Fig. 1, I provide an electric valve translating circuit for energizing a direct currentload circuit In from an alternating current supply circuit II through a transformer 12 and electric valve means l3. The transformer l2 may comprise a primary winding H connected to alternating current supply circuit H and a secondary winding IS the midpoint of which is connected to the negative terminal of load circuit in. The end terminals of secondary winding is are connected to anodes l6 and llof electric valve device l3 which is illustrated as provided with a pool type of cathode l8. Electric valve device I3 is also provided with a pair of control electrodes l9 and 20 in order to. control the output voltage of load circuit l0. Electric valve device I3 is preferably of the type employing an ionizable medium, such as a gas or a vapor, and although I have illustrated electric valve device l3 as of the multi-anode, single-cathode type, it will be understood by those skilled in the art that singleanode, single-cathode valves might equally well be used. In order to control the output voltage at load circuit Ill, an excitation circuit 2| is provided for control electrodes l9 and 20. Excitation circuit 2| comprises an plying an appreciable amount of grid current to My invention arrangement for supto alternating current supply circuit II in order that electric valve device l3 may operate in the manner of the well-known biphase rectifier. Control electrode I9 is connected in a control circuit comprising current limiting resistor 23 and impedance phase shifting circuit 24. pedance phase shifting circuit 24 comprises a pair of adjacent impedance arms 25 and 26 which may be in the form of reactors or inductors. In the instance shown, these inductors 25 and 26 comprise a voltage dividing means for the alternating potential which is impressed thereon by means of winding 2'! thus forming a transformer. The winding 2'! is preferably energized from the source of the alternating current circuit One of the remaining arms of the. impedance phase shifting device 24 comprises an electric discharge valve 26 of the high vacuum type which provides a variable resistance means while the other arm comprises a variable reactance winding 29 of the saturable type provided with two direct 5 current windings 30 and 3| the purpose of which will be hereinafter described. Similarly, control electrode 26 is connected in an excitation circuit including current limiting resistor 32 and impedance phase shifting circuit 33. phase shifting circuit 33 is substantially identical with impedance phase shifting circuit 24 described above and comprises a pair of adjacent impedance arms 34 and 35 which act as voltage dividing means for the alternating current potential which is impressed thereon by means of winding 21. One of the remaining arms of the impedance phase shifting device 33 comprises electric discharge valve 36 of the high vacuum type which provides a variable resistance means while the remaining arm comprises variable reactor 31 of the saturable type, the reactance of which is arranged to be controlled by direct current windings 30 and 3| mentioned above. Direct current winding 3| is arranged from a suitable source of direct current 38 thereby saturating the core upon which reactance windings 29 and 31, respectively. are wound. Direct current saturating winding 30 provides a regenerative arrangement for sensitivity of the phase shifting circuit and is connected in series with reactance windings 29 and 31 respectively. Winding 30 is arranged to be energized by pulses of direct current flowing through the electric discharge valves 28 and 36 respectively. Electric discharge valves 28 and 36 comprise anodes 39, cathodes 40 and control electrodes or grids 4|. The cathodes 40 of electric discharge valves 28 and 36 respectively are con nected together and also connected to the cathode |6 of electric valve device I 3. Control electrodes 4| of electric discharge valves 28 an; 35 are arranged tobe energized from the high impedance source of potential 22 through current limiting resistors 42. High impedance source 22 is illustrated as a voltage divider 43 having a movable control arm 44 connected in the grid-tocathode circuit of electric discharge valves 23 and 36 respectively. It will be understood by those skilled in the art that movable arm 44 may be This im- This impedance to be energized increasing the controlled automatically in response to an electrical condition of supply circuit I lot of load circuit in and may, for example, be controlled by relay III in accordance with the voltage of load circuit ID.

The operation of the electric valve converting apparatus illustrated in Fig. 1 is substantially as follows: The alternating potential of load-circuit H is impressed across transformer 2 and discharge paths including anodes l6 and I! alternately become conductive to transmit energy to direct current load circuit I0. Control potentials 180 electrical degrees out of phase are impressed on control electrodes l9 and 20 by virtue of phase shifting circuits 24 and 33 respectively which are arranged to be energized from alternating current circuit through a transformer comprising primary winding 2'! and a pair of secondary windings 25, 26 and 34, 35 respectively. If the potential of load circuit decreases below the predetermined constant value which it is desired to maintain, it is necessary to advance the phase of the control potentials impressed upon control electrodes l3 and 20 thereby to increase the output voltage. This may be accomplished by moving arm 44 of voltage divider 43 manually or automatically by relay ID in such a direction as to impress increased negative potentials upon control electrodes 4| of electric discharge valves 28 and 36 respectively. As the grid potentials are made more negative with respect to the cathodes, electric discharge valves 26 and 36 provide an increased resistance in phase shifting circuits 24 and 33 respectively and correspondingly less current is allowed to flow through direct current winding 30 associated with reactance means 23 and 31 respectively. Since winding 30 is wound in such a direction as to oppose the saturation effect of biasing winding 3| which tends to saturate the core upon which reactance windings 23 and 31 respectively are wound, an increase in the impedance provided by electric discharge valves 28 and 36 will cause a corresponding decrease in the impedance of reactance members 29 and 31. This results because a decrease in the current flowing in the winding 30 due to an increase in impedanceof valves 28 and 36 provides less opposition to the saturation of the core by winding 3|. As the core becomes more saturated the impedance of windings 26 and 31 de creases. Hence by increasing the variable resistance armof impedance phase shifting circuits 24 and 33 respectively and also at the same time decreasing the reactance of windings. and 31, the phase of the control potentials impressed on control electrodes l9 and 20 will be advanced thereby increasing the output voltage and restoring normal conditions. By varying the magnitude of the resistance and impedance in the parallel electric paths of the phase shifting circuit in opposite directions in response to variations in the condition controlled an amplified shift in phase of the control potential is obtained.

The operation of impedance phase shifting circuits 24 and 33 may best be understood by reference to Fig. 2 where the voltage vector E represents the potential impressed across the secondary winding sections 34 and 35 which is also in phase with the potential impressed upon the anode ll of electric valve device l3. VG represents the voltage vector of the potential impressed on control electrode 26 for a particular operating condition the phase of which may be shifted degrees in either direction from the position shown in Fig. 2. Variable reactance winding 31' is schematically shown in Fig. 2 as well as variable resistance member 36' which is representative of the electric discharge valve 36. It will be well understood by those skilled in the art that if variable resistance 36' is increased and at the same time variable reactance 31' is decreased, the grid potential Va will be rotated in a counterclockwise direction so as to be more nearly in phase with respect to the anode potential represented by E, thereby advancing the phase of the grid excitation and increasing the output voltage of load circuit It. It is to be understood that the polarity markings showing the connections with inductive windings 25, 26,

34 and 35 represent instantaneous polarities for purposes of explanation.

It will be understood by those skilled in the .art that instead of varying both the resistance and reactance elements of the impedance phase shifting devices 24- and 33, it is possible to vary only one of these elements while the other remains constant. Accordingly in Fig. 3, I have illustrated the excitation circuit 2| of Fig. 1 wherein a constant resistance element is provided in one arm of the impedance phaseshifting grid the other arm of the impedance phase shifting device is provided with variable reactance means 29, as illustrated in Fig. 1, wound upon a suitable core 46. Three direct current saturating windings are provided for the core 46 upon which reactance windings 29 and 31 are wound. Direct current saturating winding 41 is energized from a suitable source of direct current potential 48 and acts as a bias winding forsaturating the core 46. Direct current winding 49 is the control winding and may be energized from any suitable source of control potential 56 as for example from a voltage divider regulating means 43 as illustrated in Fig. 1. Direct current winding is a regenerative arran ement for amplifying the effect of control winding 49 and produces a flux in core 46 in the same direction as winding 49. The flux produced by winding 41 on the other hand opposes the flux produced by windings 49 and 5!. Suitable anode resistors 52 are provided in series with electric discharge valve 45.

Similarly, impedance phase shifting means 33 also comprises a constant resistance element illustrated as electric discharge valve 53 of the high vacuum type and resistance means 54 in series therewith. A variable resistance 55 is provided in order to control the amount of current flowing through regenerative winding 5!. The operation of the apparatus illustrat d in Fig. 3 will be readily understood by those skilled in the art from the description relating to Fig. 1. Any variation of the control or si nal potential 50 impressed on winding 49 will vary the saturation of core 46 upon which variable reactance windings 29 and 31 are wound, thus varying the current which flows through direct current winding 5| and hence producing an amplifying effect so that a small change in the control potential 50 will give a greater change in the reactance of windings 29 and 31 and hence a greater or amplified shift in the phase of the control potentials impressed on control electrodes l9 and of electric valve device I3.

Instead of varying the reactance element and allowing the resistance element to remain constant, it will be understood by those skilled in the art that one may vary the resistance element and allow the reactance element to remain constant. Accordingly in Fig. 4, I have illustrated this modification of my invention as applied to a battery charger. are characterized by the same reference numerals as in Fig. 1. The battery 56 is connected between the anode and cathode of the biphase rectifier. A holding anode circuit 51 is illustrated as-comprising a pair of holding anodes 58 and 59 connected in series with reactors 69 and 6| respectively. The holding anodes are energized from the source of alternating potential II through a suitable transformer 62. In order to obtain a control potential responsive to variations in voltage across battery 56, I have provided a circuit connected across battery 56 which includes an electric valve 63 of the glow discharge type opertaing as a constant voltage element connected in series with a resistor 64. Voltage divider 65 is also connected in parallel with battery 56 and by means of movable arm 66 it is possible to control the range of the control potentials so that batteries of different voltage may be charged with the same apparatus. Since the potential across glow discharge tube 63 is constant, any variations in battery voltage will "appear across resistor 64 and hence a control potential responsive to deviations from normal of the battery voltage may be obtained across movable arm 66 and terminal 61 which are connected across the grid-to-cathode circuit of electric discharge valves 68 and 69 acting as variable re sistors in impedance phase shifting circuits 24 and 33 respectively. A stabilizing capacitor I0 may be connected across a portion of resistor 65 if desired and a filter capacitor H may be connected across the grid-to-cathode circuit of electric discharge valves 68 and 69. Impedance phase shifting circuits 24 and 33 respectively include inductive windi'ngs 12 and I3 and fixed reactors 14 and 15 as well as windings l6 and forming the secondary winding of transformer 62. Electric discharge valves 68 and 69 are preferably of the high vacuum type and are provided with anodes 18, cathodes I9, screen grids 89 which are illustrated as connected to the cathode l8 of electric valve device l3, and control electrodes 8| connected through suitable current limiting resistors 82 to the source of control potential obtained across terminal 6] and movable arm 66. The valves 68 and 69 may also be provided with suppressor grids 8011 located between the screen grids and the plates 18.- The suppressor grids are connected to the cathodes 19 as illustrated.

The operation of the electric valve converting apparatus illustrated in Fig. 4 will be understood in view of the detailed description set forth in c nnection with Fig. 1. The electric valve de-. vice is put into operation through a suitable starting means not shown. The alternating potential from supply circuit H is c nverted to direct current for charging battery 55. If for any reasonthe voltage of the battery 56 should go above the predetermined value. a control potential will be obtained across movable arm 66 and terminal 61 which will impress a positive potential on control grids 9| thereby decreasing the resistance thereof and since no change in reactance will occur in reactors l4 and 15, reference to Fig. 2 will show that the control potentials impressed on control electrodes l9 and 29 The corresponding parts of Fig." 4

of electric discharge device II will be retarded in phase relative to the anode voltage impressed across anodes I 8 and I1 and hence the output voltage will be decreased thereby restoring normal conditions.

Figs. 5, 6, and 7 are provided to illustrate the similarity between the phase shifting impedance devices of Figs. 1 and 4. In Fig. 5 the impedance phase shifting circuit 24 of Fig. 1 is schematically represented. In Fig. 6 the phase shifting arrangement of Fig. 5 is modified so that the voltage windings 25 and 28 01' Fig. 5 have been separated and placed in a different arm of the bridge circuit 24. These are represented by reference numerals I2 and 18 respectively to correspond with the corresponding elements of Fig. 4. This amounts to an interchange of elements 14 and I8 and since the impedances of these elements are fixed, the operation of the impedance phase shifting bridge will not be changed by interchanging these elements. Fig. '7 is a modification of Fig. 6 incorporating a potential element 84' corresponding to the voltage drop across resistor 84 of Fig. 4. It' is observed therefore that the phase shiiting circuit 24 of Fig. 4 which is schematically illustrated in Fig. 7 functions in substantially the same manner as the phase shifting circuit of Fig. 1 schematically represented by Fig. 5.

In Fig. 8 I have illustrated a modification of the electric valve battery charger illustrated in Fig. 4 wherein a variable reactance element and a constant resistance element are provided in the impedance phase shifting circuits 24 and 83 respectively. A saturable reactor 82 is provided .having one reactance winding 88 connected in impedance phase shifting circuit 24 while the other reactance winding 84 is connected in one leg of impedance phase shifting circuit 83. Three saturating windings 85, 88 and 81 respectively are provided for saturable reactor 82. Saturating winding 85 is energized with a direct current control potential obtained across movable arm 88 and terminal 81 of a circuit substantially identical with that described in connection with Fig. 4. This control potential is impressed across the grid-to-cathode circuit of electric discharge valve 88 preferably of the high vacuum type provided with an anode 88, a cathode 90 and a control electrode 9|. A current limiting resistor 82 is provided in series with control electrode 8i and a filter capacitor 98 may be connected" across the grid-to-cathode circuit of electric discharge valve 88 if desired. Electric discharge valve 88 operates as a rectifier being energized with alternating potential through secondary winding 84 inductively coupled with primary winding 21 energized from alternating current supply circuit l I. In order to protect the apparatus from the high inverse voltage peaks and to absorb the induced voltage of winding 85 during the negative half cycle of winding 94, I provide electric valve 95. A direct current therefore fiows in control winding 85 which is directly responsive to variations in potential of battery 58. A constant bias potential is impressed across saturating winding 88 which may be varied by virtue of resistor 88 so as to shift the control point of the apparatus to the most sensitive position. This potential is obtained across constant voltage device 58. In order to provide a negative bias for control electrodes 18 and 20 of electric discharge device I8, I provide resistor 81 connected across battery 58 from which a suitable negative bias may be obtained by virtue of conductor 98 and impressed across the grid-to-cathode circuit of electric discharge valve IS. A suitable filter capacitor 98 may also be provided. In order to increase the amplification factor of impedance phase shifting circuits 24 and 38 when a change elements of phase shifting impedance circuits 24 and 33 respectively comprise electric discharge valves I88 and llil connected in series with resistors- I82 and I88 respectively. A variable resistor I04 is provided in order to control the amplification effect of the regenerative arrangement. If the potential of the battery 58 increases above the desired value, a potential will be obtained across movable arm 65 and terminal 81 such as to impress a negative potential on control electrode 9| of electric valve 88 with respmt to cathode 98, thereby decreasing the conductivity and hence decreasing the saturating current flowing through winding 85. A decrease in this saturating current will allow an increase in the reactance of windings 83 and 84 connected in the respective impedance phase shifting circuits 24 and 83, which, as seen by reference to Fig. 2, will cause the phase of the grid potentials impressed on control electrodes l9 and 28 to be retarded with respect to the anode potentials and hence decrease the output voltage thus restoring normal conditions. It will be understood that the regenerative winding having less direct current flowing therethrough will cause a further decrease in saturation and hence the further increase in reactance and thus ampliiy the eiIect of control potentials impressed across saturating winding 85.

While I have shown particular embodiments of my invention, it will be understood, 0! course, that I do not wish to be limited thertto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent 0! the United States is:

1. In combination, a supply circuit, electric translating apparatus, electric valve means including a control member interconnecting said supply circuit and said translating apparatus, an excitation circuit for energizing said control member to vary the conductivity 01' said electric valve means in accordance with an operating condition of said translating apparatus, said excitation circuit including parallel electric paths each including in series a source of periodic voltage and a variable impedance element, the impedance element in one of said paths comprising an electric valve and the other of said impedance elements comprising an impedance variable in response to the current conducted by said electric valve, and means for controlling the conductivity of said electric valve in response to variations in said operating condition of said translating apparatus.

2. In combination, a supply circuit, a load circuit, electric translating apparatus interconnecting said circuits for transmitting energy therebetween and comprising electric valve means having a control member, an excitation circuit for energizing said control member to vary the conductivity of said electric valve means, said excitation circuit including parallel electric paths each including in series a source of periodic potential and a variable impedance element, the impedance elementin one of said paths comprising an electric valve and the other of said impedance elements comprising a saturable reactor saturable in response to the current conducted by said electric valve, and means for controlling the conductivity of said electric valve in response to an electrical condition of one of said two first named circuits. 4

3. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus interconnecting said circuits and comprising electric valve means having a control member for controlling the conductivity thereof, an excitation circuit for energizing said control member to vary the conductivity of said electric valve means in response to an electrical condition of one of the circuits interconnected thereby, said excitation circuit including parallel electric paths each including in series a source of periodic potential and a variable impedance element, the impedance element in one of said paths comprising an electric valve having a control member and the other of said impedance elements comprising a saturable reactor having a saturating winding energized in response to the current conducted by said electric valve, and means i for controlling the conductivity of said electric valve in response to said electrical condition.

4. In combination, a supply circuit; a load circuit, electric translating apparatus interconnecting said circuits for transmitting energy therebetween and including an electric discharge valve including a control electrode, an excitation circuit for controlling the energization of said control electrode including an inductive winding providing a source of periodic potential, a control electric valve of the high vacuum type and a saturable reactor connected.in series across the end terminals of said inductive winding, an

1 output terminal intermediate the end terminals of said inductive winding, a'second output terminal intermediate said valve and said reactor,

said output terminals being connected in circuitwith the control member of said electric discharge valve, means for controlling the conductivity of said control electric valve to vary the impedance thereof, the saturation of said reactor being controlled in response to the current transmitted by said control electric valve to vary the impedance thereof to amplify the phase shift between the potential appearing across said inductive winding and the potential across said output terminals resulting from a-variation in the impedance of said control electric valve.

5. In combination, a source of periodic poten- 6. In combination an inductive winding providing a source of periodic potential, anelectric valve of the high vacuum type and a saturable reactor connected in series across the end terminals of said inductive winding, an output terminal intermediate the end terminals of said inductive winding and a second output terminalintermediate said valve and said reactor, means for controlling the conductivity of said electric valve to vary the impedance thereof, a control winding associated with said saturable reactor and energized 'in response to the current conducted by said valve for controlling the impedance thereof to amplify the .shift in phase between the potential appearing across said inductive winding and the potential across said output terminals resulting from a change in the tial including voltage dividing impedance means having an' intermediate terminal providing an output terminal, series connected impedance elements connected across saidvoltage dividing impedance means, a second outputterminal intermediate the impedance elements connected across said voltage dividing impedance means, means for varying the impedance of one of said elements, and means responsive to a change in impedance of said one element for causing a substantially simultaneous change in the impedance of the other of said elements in the reverse direction to produce an amplified shift in phase between the potential appearing across said voltage dividing impedance means and the potential across said output terminals resulting from an initial change in the impedance of said one element. r

impedance 'of saidv valve.

7. In combination, an alternating current circuit, a direct current circuit, electric translating apparatus interconnecting said circuits comprising electric valve means including a control member for controlling the conductivity thereof, an excitation circuit for energizing said control member and including a static phase shifting circuit, said phase shifting circuit including parallel electric paths, one of said paths including an electric valve of the variable impedance type having a control member and the other of saidparallel paths including a saturable reactor means for energizing the control member of said electric valve in response to an electrical condition of one of the circuit interconnected by said electric translating apparatus, and a-control winding associated with said saturable reactor and energized in response to the current transmitted by said electric valve to decrease the impedance of said saturable reactor as the impedance of said electric valve increases to produce an amplified shift in phase of the potential supplied to the control member of said electric valve means in response to a variation in said electrical condition.

, 8. In combination, a supply circuit, a load circuit, electric translating apparatus interconnecting said circuits comprising electric valve means including a control electrode, an excitation circuit for energizing said control electrode to control the output of said electric valve means, said excitation circuit including a static phase shifting circuit for impressing on said control electrode a periodic potential having a phase relation with respect to the anode-cathode potential of said electric valve means which is variable in response to an electrical condition of one of the circuits interconnected by said electric translating apparatus, said phase shifting circuit including parallel branches each of which comprises a source of periodic potential and an impedance element in series, one of said impedance- V supplied to the control member of said electric apparatus interconnecting said transmitting energy therebetween and comprisvalve means in response to variations in said electrical condition.

9. In combination, an alternating current circuit, a direct current circuit, electric translatin circuits for in series circuit relation with the cathode and control electrode 01 each oi said electric discharge valves, and means for controlling the impedance of one 01' said impedance elements in response to an electrical condition of one or said first two named circuits to control the phase of the potential appearing between said output terminals with respect to the phase of said periodic potential.

10. In combination, a supply circuit, a load circuit, electric translating apparatus interconnecting said circuits for transmitting energy therebetween and including electric valve means having a control electrode and a holding anode, a circuit for controlling the energization of said control member and said holding anode including a phase shifting network having parallel electric paths, each oi said paths including a source oi periodic potential and an impedance element, said impedance elements and saidsources of periodic potential being connected in alternate re lation, means connecting the common terminal of oneoi said impedance elements and one of said sources of potential with said control member, means connecting the common terminal of said impedance element and the other of said sources of periodic potential to said holding anode, and means for controlling one of said impedance elements in response to an electrical condition or one of said circuits to control the energization ot-said control member.

11. In combination, a supply circuit, a load circult, electric translating apparatus interconnectingsaid circuits comprising electric valve means including a control member, means for controlling the energization of said control member in response to an electrical condition of one or the circuits interconnected by said translating ap-' paratus including parallel electric paths each ineluding a source of periodic potential and an impedance element, one 01' said impedance elements comprising a saturable reactor having a control winding energized in response to said electrical condition to vary the saturation of said reactor, and a second winding energized in response to the magnitude or current flowing in said saturable reactor to amplify the phase shift of said periodic potential resulting from the variation in said electrical condition.

12. In combination, a supply circuit, electric translating apparatus connected for energization from said circuit and including electric valve means having a control member, a control circuit for controlling the energization of said control member including a variable impedance element, means responsive to an operating condition oi said translating apparatus for varying the impedance of said element, and mean responsive to a change in impedance of said element for further altering said impedance in the same direction to amplify the impedance change in said element occurring in response to a variation in said operating condition, said impedance element being connected in the energizing circuit of said control member to vary the excitation thereof in response to variation in said electrical condition.

13. In combination, a supply circuit, a load circuit, electric translating apparatu interconnecting said circuits for transmitting energy therebetween including a plurality .of electric discharge valves each including a control member, a static phase shifting network for controlling the excitation or said control members including parallel electric paths each including a source 0! periodic potential and an impedance element, one of said impedance elements comprising a saturable reactor including a biasing winding for normally saturating, the core of said reactor, a control winding tending to overcome the eiiect of said biasing winding and energized in response to variations in an electrical condition in one of said circuits, and an additional winding energized in response to the current conducted by said saturable reactor for producing a magnetomotive force in the same direction as said control winding to produce an amplified change in impedance of said saturable reactor in response to variations in said electrical condition.

ELMO E. MOYER. 

